The present invention relates to bearing assemblies having an inner race and an outer race with a plurality of ball bearings between the races, and more particularly to such bearing assemblies which are intended for applications involving moderate loads and speeds, and requiring long bearing lifetime yet for which the manufacturing expense of precision grinding or other secondary operation is not justified. Such bearings are used, for example, in the roller assemblies of conveyors, in washing machines, and in the wheel assemblies of motorized lawn and garden equipment to support a cantilevered load, and in the hinges of large doors.
For such applications, it is desirable to fabricate an inexpensive bearing as a single assembly for shipment and installation into the end product, to assure that the ball bearings are not dispersed. However, because of the hardness required on ball races, the steel of such bearings is quite brittle and the ball races cannot be flexed so as to snap together without fracturing.
FIGS. 1A, 1B show sections through several hardened bearing assemblies of the prior art which provide a unitary bearing assembly for shipment and installation. As shown in FIG. 1A, a bearing assembly 1 includes a first race 2, a second race 3 and a plurality of bearings 4 between the races, with a jacket 5 holding the two races together. Jacket 5 serves to secure the bearing assembly together during shipment but is designed to fit within a housing so as to permit direct pressure-transmitting contact with the races from the components being supported.
FIG. 1B shows another prior art bearing 10 of relatively small dimension having a stamped inner race 12 and a stamped outer race 13 with a plurality of bearings 14 held therebetween. A tubular neck 15 of the inner race extends through the center of the outer portion, and is flared or punched out at one or more discrete points 15a after assembly of the bearing to retain the outer race 13 on the neck 15. In this prior art bearing the races are stamped from a relatively soft sheet stock, and, following assembly, the entire bearing assembly is heat treated to harden the bearing surfaces. Such hardening of a completed assembly is less effective than treatment of the races separately, which permits a more uniform and deeper exposure to the hardening environment. Nonetheless, post-assembly hardening is required in this embodiment because the punching operation for making the retaining flare or bulges 15a would shatter a prehardened race.